The present invention relates to the field of perfumery. It relates, more particularly, to a device for diffusing perfume into the surrounding air. The device of the invention, however, can also be used for the diffusion of other active volatile agents, such as insect repellents, deodorizing or sanitizing agents, amongst others.
The use of various devices for the diffusion of volatile compounds, for example perfumes, sanitizing agents, insect repellents, and the like, has become more and more current in recent years. For example, air-freshening devices or deodorizers are currently used in practically all households to mask bad odours or to impart fragrances to the ambient air. The known devices used for the diffusion of volatile compounds into the surroundings make use of various principles. As an example, one can mention here dispersing devices of the spray type, aerosols or mechanical. Other examples include plastic packing elements enclosing the active ingredients in liquid form. Typically, the diffusion of the active ingredient takes place through membranes permeable to the vapours of said ingredient.
One class of systems capable of diffusing active volatile ingredients and which are of relevance with respect to the present invention are solid state devices consisting of solid materials or carriers impregnated with an active ingredient. Such devices may be formed of various materials which are capable of absorbing the ingredient and subsequently releasing it in a more or less controlled manner. Examples of such known materials include gels, such as agar-agar or sodium stearate gels, synthetic polymer resins, or blocks of mineral material, e.g. plaster or silica. It is even possible, for some purposes, to have active ingredients absorbed on paper or cardboard in order to obtain a more or less solid carrier device for diffusing the volatile ingredient thus absorbed. Often, solid devices are designed to be non-wetting, i.e. to be capable of effectively retaining the liquid active volatile material and only allowing the diffusion of the vapours of said material.
Solid state air-freshener devices have the advantage that they are easy to handle and may be shaped into various forms adapted to the customers"" needs and desires. The devices can for example be in the form of a solid block of a particular shape, e.g. a figure or a geometrical form, and be used as such. A material often used for such devices is plaster, allowing an easy shaping of the raw material into the desired form.
Solid state devices can also be placed into a housing in which they are typically covered by a lid or a grill having openings to allow for communication between the surrounding air and the perfumed solid block, or they can be arranged between two grills. In these applications, the solid perfumed block is covered by said lid or said grill and is sometimes invisible from the outside of the packing. Unlike the unhoused air-fresheners, the appearance of the latter air-freshening devices is that given by the housing or the grill, and it is therefore not necessary, or not even possible, to shape the solid block into a particular form to cause an aesthetic impression.
Solid block perfuming devices, however, generally have the drawback that the vapour release rate is not constant, but drops dramatically within the lifetime of the product. Furthermore, often the device is already exhausted, i.e. no longer diffuses sufficient active ingredient, in spite of the fact that considerable amounts of active ingredient still remain in the core of the block. This residual perfume, retained by the material of the block, is therefore entirely lost.
The object of the present invention is to provide a solid air-freshening device for diffusing volatile substances, e.g. perfumes, insect repellents, deodorizing or sanitizing agents, which is capable of diffusing said volatile substances at a relatively constant rate throughout the lifetime of the device. Furthermore, the devices of the invention are capable of releasing practically their entire content of volatile substance within their effective lifetime, such that very little active ingredient will be retained as a residue.
Accordingly, the present invention provides a device for the diffusion of an active volatile substance into ambient air or closed spaces comprising a solid casing or housing and a solid carrier containing said volatile substance wherein said solid carrier is arranged in at least one recess formed in the housing, the at least one recess having a depth and a width which are chosen in relation to the composition of the solid carrier containing the active substance so that the ratio of the evaporation surface of the solid carrier to the mass of the solid carrier disposed within the said recess is such that a substantially constant vapour release rate and total evaporation of said active volatile substance during the active lifetime of the device is obtained.
The term xe2x80x9clifetimexe2x80x9d in relation to the diffusion device of the present invention is used here to designate the period of time during which the device diffuses an amount of active ingredient sufficient to be effective, i.e. which, for example, can be perceived in the case of perfumes, or can remain active as insect repellent, deodorizing or sanitizing agent, and the like.